Typically, a solid oxide fuel cell (SOFC) employs a solid electrolyte made of an ion-conductive oxide such as stabilized zirconia. The electrolyte is interposed between an anode and a cathode to form an electrolyte electrode assembly (hereinafter also referred to as an MEA). The electrolyte electrode assembly is interposed between separators (bipolar plates). During use thereof, generally, a predetermined number of the electrolyte electrode assemblies and the separators are stacked together to form a fuel cell stack.
As a system including this type of fuel cell stack, for example, the fuel cell battery disclosed in Japanese Laid-Open Patent Publication No. 2001-236980 (hereinafter referred to as conventional technique 1) is known. As shown in FIG. 9, the fuel cell battery includes a fuel cell stack 1a, and a heat insulating sleeve 2a provided at one end of the fuel cell stack 1a. A reaction device 4a is provided in the heat insulating sleeve 2a. The reaction device 4a includes a heat exchanger 3a. 
In the reaction device 4a, as a treatment for a liquid fuel, partial oxidation reforming, which does not use water, is performed. After the liquid fuel is evaporated by an exhaust gas, the liquid fuel passes through a feeding point 5a, which forms part of the heat exchanger 3a. The fuel contacts an oxygen carrier gas heated by the exhaust gas to induce partial oxidation reforming, and thereafter, the fuel is supplied to the fuel cell stack 1a. 
Further, as shown in FIG. 10, the solid oxide fuel cell disclosed in Japanese Laid-Open Patent Publication No. 2010-504607 (PCT) (hereinafter referred to as conventional technique 2) has a heat exchanger 2b including a cell core 1b. The heat exchanger 2b heats air at the cathode utilizing waste heat.
Further, as shown in FIG. 11, the fuel cell system disclosed in Japanese Laid-Open Patent Publication No. 2004-288434 (hereinafter referred to as conventional technique 3) includes a first area 1c having a vertically extending columnar shape, and an annular second area 2c disposed around the first area 1c, an annular third area 3c disposed around the second area 2c, and an annular fourth area 4c disposed around the third area 3c. 
A burner 5c is provided in the first area 1c, and a reforming pipe 6c is provided in the second area 2c. A water evaporator 7c is provided in the third area 3c, and a CO shift converter 8c is provided in the fourth area 4c. 